This invention relates generally to ceramic superconducting compositions and is particularly directed to a method and apparatus for extruding metal oxide ceramic superconducting compositions in the form of thin wires, tubes or ribbons.
Work has intensified on a new class of ceramics since the discovery several years ago that these materials exhibit superconductivity at unprecedented high temperatures. No longer is it required to maintain exotic materials at liquid helium temperatures to realize superconductivity. Ceramic metal oxide conductors have exhibited superconducting properties at temperatures as high as 125 K. It is of course desirable for a superconductor to have a high critical current density to allow it to conduct large currents while remaining superconductive. It is also highly desirable for the superconducting material to possess physical characteristics which facilitate its formation in commercially usable forms. Superconducting materials shaped into usable forms such as thin wires and strands are brittle, weak and of only limited flexibility. Attempts to produce very small diameter superconducting wires which are believed to be more flexible and could be combined in a larger braid or a multistrand arrangement for greater current carrying capacities have also met with only limited success.
The present invention addresses the aforementioned limitations of the prior art by providing apparatus and method for fabricating small diameter wires on the order of 10 mils having enhanced flexibility while retaining superconducting electrical properties at high temperatures. The present invention is directed to an extrusion process employing various die arrangements for forming a metal oxide ceramic comprised of YBa.sub.2 Cu.sub.3 O.sub.7-x into thin wires, tubes or ribbons.